The expansion of an underground coal mine requires digging a tunnel that initially has an unsupported roof. To provide support for the roof, a rotary drill bit (e.g., a roof drill bit) is used to drill boreholes, which can extend from between about two feet to about (or even greater than) twenty feet, into the earth strata. Roof bolts are affixed within the boreholes and a roof support (e.g., a roof panel) is then attached to the roof bolts. Examples of a conventional roof drill bit with an axial forward slot that carries a blade style hard insert are shown in U.S. Pat. No. 5,172,775 to Sheirer et al.
It is desirable to provide a roof drill bit that permits completion of the drilling operation as soon as possible. A roof drill bit that presents at least three leading cutting edges increases the penetration rate due to an increase in the number of the leading cutting edges. Three leading cutting edges, especially with a radial orientation, permits the roof drill bit to advance forward with very little the roof drill bit to advance forward with very little wobble (i.e., side-to-side movement) so as to achieve balanced drilling. Leading cutting edges that terminate short (i.e., at a point radially outward) of the center point of the hard insert define a central open area so as to reduce the amount of low velocity cutting, i.e., the cutting action that occurs nearer to the center point. An increase in the number of the leading cutting edges, the balanced drilling, and the reduction in low velocity drilling each contributes to an increase in the penetration rate of the roof drill bit, which provides for the efficient completion of the drilling operation.
Clogging and stalling may occur when drilling at a higher penetration rate. It would be an advantage to adequately handle and evacuate debris so as to reduce the potential for clogging. A roof bit drill that pulverize earth strata at the tip of the bit into manageable small sized particles that can be easily evacuated. It would be an advantage to provide a roof drill bit with a drill bit body that can withstand the stresses inherent during stalling.